Omeprazole is a well known pharmaceutical useful for inhibiting gastric acid secretion and for providing gastrointestinal cytoprotection effects in man. It may be used for prevention and treatment of gastrointestinal inflammatory disorders, including gastritis, gastric ulcer and duodenal ulcer. Chemically omeprazole is 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1H- benzimidazole, of formula I: ##STR1##
Various basic salts of omeprazole, such as omeprazole magnesium and omeprazole sodium, are known and described in the patent and scientific literature. Magnesium omeprazole is an example of what are called basic salts or basic addition salts of omeprazole, these terms being used herein synonymously. Magnesium omeprazole, as the term is used herein, means salts formed between one magnesium di-cation and two omeprazole anions. These salts may contain water of hydration, residual organic solvents, traces of free base omeprazole and traces of inorganic salt impurities.
A problem with omeprazole is its stability characteristics. Upon storage without any precautions being taken, it is reported to be degraded at an undesirably high rate. During storage under accelerated stability conditions, e.g. at 37.degree. C. and a relative humidity of 80% for a period of six months, about 6% of the substance is converted to degradation products. Although decomposition under normal storage conditions is lower, it is desirable to obtain omeprazole derivatives which exhibit improved stability.